1. Field of the Invention
The present invention relates in general to communication systems, and more particularly, to a method and system for measuring/estimating the relative skew between clocks in a packet based communication networks.
2. Description of Related Art
Estimating the relative skew between clocks on different host machines (or referred to network nodes) in a packet network environment, such as the Internet, is relatively new since real-time applications and usage based pricing are relatively new concepts. The issue of measuring one way transit times of packets is becoming increasingly important with the emergence of real-time applications such as voice and video over the Internet. This concept of one-way transit time measurements involves comparing (specifically, taking differences of) times measured with respect to different clocks (e.g. the sender and receiver clocks). Two of the main sources of clock timing discrepancy are offset and skew. Offsets can be readily corrected. The most widely used remedy for clock offsets is a form of synchronization (e.g. using Network Time Protocol (NTP), or Global Positioning System (GPS), etc.). It should be noted, though, this synchronization zeros the clock difference between two clocks at one instant, but the clock skew will inherently cause the clocks to drift apart as time progresses. Accordingly, a clock skew can impose a serious clock timing discrepancy problem for a real-time application.
Accordingly, there is a need to develop a method to detect/correct clock skews. Specifically, there is a need to develop a method of measuring/estimating the relative skew between clocks on different host machines (or referred to network nodes) in a packet network environment such as the Internet. The present invention provides a solution to the above and other problems and offers advantages over the existing network systems.